Effect of cobalt substitution on magnetic properties and microstructure of nanocrystalline （NdDyTb）12.3（FeZrNbCu）81.7B6.0 ribbons

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdOyTb)12.3(FeZrNbCu)81.7CoxB6(x=0-15) ribbons prepared by rapid quenching and subsequent annealing was systematically investi-gated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization Jr and maximum en-ergy product (BH)max increased with increasing x from 0 to 12 and then decreased for x=lS. The intrinsic coercivity Hci of (NdDyTb)12.3 (FeZrNbCU)81.7-xCoxB6 ribbons optimally processed decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15. Optimum magnetic properties with Jr=1.041 T, Hci=944.9 kA/m and (BH)max=155.1 kJ/m3 were achieved by annealing melt-spun ribbon (x=-12) at 675℃ for 10 min. There was no significant influence of Co substitution on microstructure.     

Structure and permanent magnetic properties of SmFex （x=3-8） melt spun ribbons during heat treatment

Compounds with the composition SmFex（x=3–8） were prepared by melt spun method at a velocity of 40 m/s and subsequent annealing at temperature between 600–1000 ℃. The crystal structures of the as-quenched and as annealed powders were investigated by XRD methods with following Rietveld analysis. The glass forming ability could be enhanced by the increase of Sm content to x≤5.Metastable Sm5Fe17-type structure existed when 3≤x≤5 and temperature was lower than 800 ℃. SmFe2-type structure could be stable up to 1000 ℃ when x〉3 and temperature was under 800 ℃. The content of SmFe2-type decreased with the increase of x value and increased with temperature lower than 800 ℃, from which SmFe2-type started to bring the transition to SmFe3-type. As for Sm5Fe17-type compounds with x=3.4, the highest coercivity of 33.6 kOe could be obtained under a velocity of 30 m/s and heat treated under 700 ℃×1h.